The above differences have an immediate impact on candidate pairing
mechanism of the superconductivity. At critical doping, the \(t\) -\(J\) -\(K\) 
model predicted possible SC transition from a gapped (\(d+is\) )-wave state to
a gapless \(d\) -wave pairing state due to the competition of Kondo and
superexchange interactions [1]}. Latest scanning tunneling
experiment (STM) also revealed two different gap structures of U and
V-shapes, supporting the possibility of above scenario. Thus, nickelates may
belong to a novel class of unconventional superconductors and one may
anticipate potentially more interesting properties bridging the cuprates and
heavy fermions.
